The invention relates to a method for determining the fatigue of a pump rotor of a fast rotating gas turbopump.
Gas turbopumps and especially turbo molecular pumps are operated at rather high rotational speeds of 10,000-100,000 rpm. Because of the great centrifugal forces, temperature influences etc., the pump rotor is subject to me-chanical fatigue. In particular with gas turbopumps, narrow gaps are provided between the pump rotor and the pump stator so as to obtain as high a capacity as possible. After a certain time, the pump rotor fatigue causes a failure of the pump rotor or a collision of the pump stator and the pump rotor. In order to avoid this, the pump rotor is replaced prior to the estimated time of collision.
A chronologically constant maintenance interval may be provided that schedules maintenance work or a replacement of the pump rotor after a certain time or a certain operation period.
From DE 101 51 682 A1, a method is known wherein a dynamic maintenance interval is calculated from the absolute rotational speed and the temperature of the pump rotor. The so-called creep stress of the pump rotor is thus determined and is included in the calculation of the dynamic maintenance interval. Studies have shown that, in this manner alone, a practice-oriented dynamic maintenance interval cannot be determined with sufficient accuracy, given certain operational conditions.